[neon-notifications] Dev Required: ostree - 2021.5

[Neon CI]

https://build.neon.kde.org/job/watcher_release_backports-focal_ostree/17/display/redirect

#<Debian::UScan::DEHS::Package:0x0000557d8dd34108 @name="ostree", @debian_uversion="2020.8", @debian_mangled_uversion="2020.8", @upstream_version="2021.5", @upstream_url="https://github.com/ostreedev/ostree/releases/download/v2021.5/libostree-2021.5.tar.xz", @status="Newer version available">